Coatino composition containing



Reiesued Dec. 7, 1943 COATING COMPOSITION CONTAINING POLYVINYL ACETATEMETHYLAL Robert 0.. Swain, Riverside, and Pierrepont Adams. Glenbrook.Conn assignors to American Cyanarnid Company, New York, corporation ofMaine No Drawing. Original No. 2.32am. dated August 10. 1943.8erlal No.371,183. December as. 1940. Application tor reissue September 27, 1943,I

Serial No. 504.000

3 Claims. ('01. 260-42) This invention relates to coating compositionscontaining polyvinyl acetate methylai and melamine-formaldehyde resins.

An object of this invention is to improve the physical and chemicalproperties of coating compositions containing polyvinyl acetatemethylal, e. g., chemical resistance such as acid resistance, heatresistance. etc.

Another object 01' this invention is to provide compositions containingpolyvinyl acetate methylal and compatible proportions of compatiblemelamine-formaldehyde resins.

These and other obiects are attained by blending polyvinyl acetatemethylal with not more than about 40% (total solids weight basis) of amelamine-formaldehyde resin which has been aikylated with a butylalcohol or benzyl alcohol wherein the molal ratio of formaldehyde tomela- V mine is at least about 4:1. i

The following examples in which the proportions are in parts by weightare given by way of illustration and not in limitation.

The polyvinyl acetate methyial used in the ioliowingexamples is aproduct sold under the trade name oi l 'ormvar by Shawinigan ProductsCorporation. Polyvinyl acetate methylal resins may be produced byreactinsmlyvinyi acetate with formaldehyde asdescribed for example inthe patent to Morrison et al., U. 8. sue No. 20,430.

trample 1 Parts Melamine-formaldehyde resin A".......... 10 Polyvinylacetate metbylal (Pomvaf')---'. 80 A composition containing these isprepared by admixing parts of melamineiormaldehyde resin A solutionresin) with mpartsoi'polyvinyi amatemethylalstockeolution" (containing10% of polyvinyl acetate methylal and of dioxane); Films of thecomposition are applied to metal objects and baked at a temperature ofabout C. for about one-half hour. The product is a hard. transparentcoating havind 800d iiim strength.

trample 2 g Parts Melamine-formaldehyde resin B"..- 25 Polyvinyl acetatemetlwlal (l'brmvar) I5 Acompoeifloncontainingtbeceingredientsis prepar dradnuxinseopartsormeiamineposition ientltantiallyanhydrousappliedtometalobiectsaudbakedatatemper- I turewiiibeaboutiM-m',

ature of about 135' C. for about one-half hour.

A clear, tough film is formed.

Example 3 7 Parts Melamine-formaldehyde resin "C" 10 Polyvinyl acetatemethylal ("Formvar) 90 Example 4 4 Parts Melamine-formaldehyde resin D25 Polyvinyl acetate methylal ("Formvar") 75 A composition containingthese ingredients is prepared by admixing 50 parts ofmelamineformaldehyde resin D solution (50% resin) and 750 parts of"polyvinyl acetate methylal stock solution. Films of the composition areapplied to metal objects and baked at a temperature 0! about C. forabout one-half hour.

' A water-white illm having good chemical properties is iormed.Preparation of melamine-formaldehyde resin "A" Parts Melamine (1 mo1)...128 Formalin (4 mols) (37% formaldehyde in waterThismixtureisplacedinarefluxapparatuswhichieprovidedwithaandasuitablewater trapflarcmghwhich the refluxcondensatepasscs onitsreturntothereactionchamberandinwhich theessentially aqueous traction oi thecondensatemaybeeeparatedimmtheessentiallynonaqueomiractionandmeansisprovidedsothattheiormertractionmaybe drawn'oiliidesirable.'rhereactionmixtureisrenuxedatatemperature oiabout 91-03 C. atatmosphericpres sureiorG-flhours. 'I'hewaterisremovedbydistlllationiromthereactionminture duringflaereiiuxoperationpreierahlyatterabontfl-ohomshaveelapecdandthewater so removed is separated ironthe reflux eondemateinthewatertrap. nm'lng thedisflllapi'alureilloweredsufllciently to reduce the vapor temperature to about 85-90 C. and theresin solution is concentrated to about 60-70% solids by vacuumdistillation. The resulting resin solution may be diluted to about 50%solids with any desired solvent or diluent, e. g., xylene.

Preparation of melamineformaldehyde resin "B" Parts Melamine (1 mol) 126Formalin (5 mols) (37% formaldehyde in water) 405.5 n-Butanol 440 Thismixture is placed in a reflux apparatus which is provided with acondenser and a suitable water trap through which the refiux condensatepasses on its return to the reaction chamber and in which theessentially aqueous fraction of the condensate may be separated from theessentially nonaqueous fraction and means is provided so that the formerfraction may be drawn on if desirable. The reaction mixture is refluxedat a temperature of about 91-93 C. at atmospheric pressure for 6-12hours. The water is removed by azeotropic distillation from the reactionmixture during the reflux operation beginning preferably after about 2-5hours have elapsed and the water so removed is separated from the refluxcondensate in the water trap. During the distillation about 550additional parts of butanol are added gradually. When the refluxcondensate is substantially anhydrous the vapor temperature Will beabout 100-105" C. The pressure is lowered sufficiently to reduce thevapor temperature to about 85-90 C. and the resin solution isconcentrated to about 60-70% solids by vacuum distillation. Theresulting resin solution may be diluted to about 50% solids with anydesired solvent or diluent. e. g., xylene.

Preparation of malamine-formaldehyde This mixture is placed in a refluxapparatus which is provided with a condenser and a suitable water trapthrough which the reflux condensate passes on its return to the reactionchamber and in which the essentially aqueous fraction of the condensatemay be separated from the essentially non-aqueous fraction and means isprovided so that the former traction may be drawn 0!! if desirable. Thereaction mixture is refluxed at a temperature of about 91-93 C. atatmospheric pressure for 6-12 hours. The water is removed by azeotropicdistillation from reaction mixture during the reflux operation beginningpreferably after about 2-5 hours have elapsed and the water so removedis separated from the reflux condensate in the water trap. During thedistillation about 550 additional parts of butanol are added gradually.When the reflux condensate is substantially anhydrous the vaportemperature will be about 100-105C. The pressure is lowered sumeientlyto reduce the vapor temperature to about 85-90 C. and the resin solutionis concentrated to about 60-70% solids by vacuum distillation. Theresulting resin solution may be diluted to about 50% solids with anydesired solvent or diluent. e. 8., xylene.

Preparation 0! melamine-formaldehyde resin "D Parts Melamine (1 mol) 126Formalin (5 mols) (37% formaldehyde in water) 405.5 Benzyl alcohol 600means is provided so that the former fraction may be drawn off ifdesirable. The reaction mixture is refluxed at a temperature of about93-95-C. at atmospheric pressure for 6-12 hours. The water is removed byazcotropic distillation from the reaction mixture during the refluxoperation beginning preferably after about 2-5 hours have elapsed andthe water so removed is separated from the reflux condensate in thewater trap. When the reflux condensate is substantially anhydrous thevapor temperature will be about IOU-105 C. The pressure is loweredsufficiently to reduce the vapor temperature to about 95-90 C. and theresin solution is concentrated to about 60-70% solids by vacuumdistillation. The resulting resin solution may be diluted to about 50%solids with any desired solvent or diluent, e. g., xylene.

Alkylated melamine-formaldehyde resins may be produced in accordancewith the procedures outlined above, as well'as in any other suitablemanner. Aqueous syrups of melamine-formaldehyde resins may be firstproduced and then alkylated either simultaneously with dehydration orsubsequent to dehydration. Generally the simultaneous condensation ofmelamine, formaldehyde and a suitable alcohol is used because ofconvenience. The condensation may be carried out either with or withoutan acid catalyst and in some instances basic catalysts may desirably beutilized.

The melamine formaldehyde resins vary slightly according to minorvariations of control during their production and in some instancessmall proportions of a suitable solvent material, e. g., dioxane,acetone, acetone-alcohol mixtures, the monoethyl ether of ethyleneglycol (Cellosolve"), etc., may be added to the original solutions ofpolyvinyl acetate methylal and melamine-formaldehyde resin in order toproduce perfectly clear solutions if such solutions are not originallyobtained.

While formaldehyde has been used in the previous examples, it will beobvious that other aldehydes such as the various polymers offormaldehyde, e. g., paraformaldehyde, or substances which yieldformaldehyde may be used in place 01' part or all of the formaldehyde.

As indicated by the above examples polyvinyl acetate methylal has beenfound to be compatible with not more than about 40% oi amelaminelformaldehyde resin alkylated with butyl and benzyl alcohols,wherein the molal ratio or formaldehyde to melamine is at least about4:1. Melamine-formaldehyde resins which have been alkylated with hexyland octyl alcohols are compatible with polyvinyl acetate methylal inproportions up to about 10% and butylated melamine-formaldehyde resinswherein the molal ratio of formaldehyde to melamine is 5:1 arecompatible in proportions as high as about 60%. While higher ratios offormaldehyde to melamine than 6:1 may be used, it is generallyundesirable inasmuch as formaldehyde is lost during the curing so thatusually the product in its cured condition does not contain more thanabout 6 mols of formaldehyde to 1 mol of melamine. The percentagecomposition in each instance in this paragraph is on a total solidsweight basis.'

The melamine-formaldehyde resins may be alkylated with benzyl alcoholand with n-butyl alcohol as in the above examples or they may bealkylated with other butyl alcohols or mixtures of any oi thesealcohols. The term alkylated melamine-formaldehyde resin is intended todenote compositions which are reacted with an alcohol.

Our products may be plasticized with a wide variety of materials such asthe alkyl phthalates. tricresyl phosphate, fatty acid amides, variousalkyd'resins, etc.

Various fillers, pigments, dyes and lakes may be added to ourcompositions, e. g., lithopone,

zinc oxide, titanium oxide, ferric oxide, Prussian trocellulose, etc..as well as in varnishes, especially drying oil varnishes, such as thosefrom tung oil, linseed oil, etc. I

Our products may be used in lacquers and other coating compositionsincluding enamels, paints, etc. They ar particularly suitable for wirecoating and for the production of insulating materials. Our mixtures maybe. applied to paper, cloth and the'like and the resulting product maybe used for a wide variety of purposes. Films of our materials may beused in the production of photographic films. Our. compositions are alsosuitable as adhesives such as for shatterprooi glass and they may alsobe used in the manufacture of filaments, sheets, etc.

The melamine-formaldehyde resins improve the chemical resistance such asacid resistance, of polyvinyl acetate methylal resins and our mixtureshave improved color retention upon heating. Another importantimprovement in polyvinyl acetate methylal resins which is achieved bythe incorporation of melamine-formaldehyde resins is the reduction inthe thermoplastlcity thereof. In some instances the polyvinyl acetatemethylal resin may exhibit a toughening effect upon themelamine-formaldehyde resins.

The term compatibie" as used herein is intended to denote compositions,films of which are clear and homogeneous after baking.

Obviously many modifications and variations in the processes andcompositions described above may be made without departing from thespiri and scope of the invention as defined in the appended claims. Weclaim: 1. A coating composition containing polyvinyl 2s acetate methylaiand a melamine-formaldehyde resin which has been heated until reactedwith an alcohol selected from the group consisting of butyl alcohols andbenzyl alcohol, wherein the molal ratio of formaldehyde to melamine i atleast about 4:1 and wherein the weight ratio of polyvinyl acetatemethylal to melamine resin is at least about 3 :2.

2. A coating composition containing polyvinyl acetate methylal and amelamine-formaldehyde resin which has been heated until reacted withn-butyl alcohol, wherein the molal ratio of formaldehyde to melamine isat least about 4:1 and wherein the weight ratio or polyvinyl acetatemethylal to melamine resin is at least about 8:2.

3. A coating composition containing P lyvinyl acetate methylal and amelamine-formaldehyde resin which has been heated until reacted withbenzyl alcohol, wherein the 'molal ratio or formaldehyde to melamine isat least about 4:1 and wherein the weight ratio of polyvinyl acetatemethylal to melamine resin is at least about 3:2.

ROBERT C. SWAIN. PIERREPONT ADAMS;

CERTIFICATE orflcomcrrqn. {Reieeue 1m. 22,1;02. Decepber 7,- 191 ROBERT0. mm, 21' AL.

It is hereby certified thet error appears in the printed epeciricetionor the above numbered p tent requiring correction ae rollers: Page 2,eec- 0nd column, line 2a, for "95-90 c.'-rua'--e5-9o c.--; and that the"in Letters Petent be reed with this correction therein that the hemeoontom to the record of the cue in the Patent Office.

Signed and .154 um- 8th 'day or February, A. 1). 191m.

Henry Ven" Arednle, (8011) Acting commissioner ot retegteb

